1) That's the RDF (Radio Direction Finder) Loop.
2) Possible, but hard, esp the Flak exam.
It can be done though. It's not a requirement to complete them.
3) Shift+F2 (or free cam) will work and no known issues exist to date. Just don't go out of bounds.
4) GWX Hydropone sounds are distinctive. You'll know them when you hear them. There is no current GWX sound tutorial however, the easiest way is to determine the differences while in game. You only need to worry about the difference between Warships & Merchants, the rest are very easy to classify.